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NIOSH Update:

Noise from stock cars at racing events can reach levels associated with work-related risks to hearing, researchers from the National Institute for Occupational Safety and Health (NIOSH) describe in a NIOSH Science Blog posted today. The scientists, Chucri A. (Chuck) Kardous and Thais Morata, suggested precautions for drivers, pit crews, and workers in the stands, based on NIOSH recommendations for preventing work- related hearing loss. The blog is posted at http://www.cdc.gov/niosh/blog/.

In measurements last year at three NASCAR tracks, the NIOSH researchers found that noise levels often exceeded those in some of the noisiest industrial settings. The loudest noise was measured at the Bristol (Tenn.) Motor Speedway, where racers will compete Aug. 21 in the 2010 Sprint Cup series. "Bristol has developed a reputation among fans to be the noisiest track on the NASCAR circuit," the researchers said in the Science Blog. "This is mainly due to its bowlshaped layout (similar to a football stadium), small track size, and metal-constructed stands that reverberate and amplify the noise generated by the stock cars."

Overall during race preparation, practice, qualification, and competition, the noise at Bristol exceeded NIOSH’s recommended exposure limit. This limit in technical terms is 85 decibels, Aweighted (85 dBA) as an average of measurements over eight hours. This is the NIOSH recommended limit for preventing work-related, noise-induced hearing loss. The noise levels at Bristol ranged from 96 dBA in the stands to 114 dBA for a driver inside a car during practice.
The loudest noise levels were found in the pit area. At Bristol and the two other tracks where noise was measured - the Indianapolis (Ind.) Motor Speedway and the Kentucky Speedway in Sparta, Ky. - peak noise levels in the pit reached or exceeded 130 dB, a level often recognized as the human hearing threshold for pain.

"Drivers, pit crews, and other workers at NASCAR’s tracks are justifiably proud of being part of a tradition that millions of people enjoy. At the same time, it is important to be aware that occupational exposures to excessive noise can lead to hearing impairment and tinnitus, and that protections are available and recommended for lessening this risk," NIOSH Director John Howard, M.D., said of the research findings.

NIOSH recommends that work-related noise be engineered out of a process as a first line of defense. If mufflers are not used to reduce noise from race cars to a time-weighted average of 85 dBA, then hearing protection should be used by drivers and crew members, the researchers said. They recommended custom-molded earplugs with built-in speakers, a type of protection currently provided to drivers.

Workers elsewhere at tracks should be made aware of the potential hazards of noise through educational and informational campaigns, the researchers said. Such campaigns also would be of value to spectators, who are likely to be exposed to the same levels of noise as workers in the stands. The blog discussion grew from research that began with an evaluation of work-related exposures to noise and chemicals at the Bristol track, in partnership with a stock car racing team. The research subsequently expanded to include the two other tracks. The data were also reported earlier this year in a peer-reviewed scientific journal for noise control professionals. The NIOSH Science Blog is one of NIOSH’s means for reporting its research to a wider audience and stimulating scientific research into practice.

NIOSH is the federal agency that conducts research and makes recommendations for preventing work-related injuries and illnesses. It was created under the Occupational Safety and Health Act, and is part of the U.S. Centers for Disease Control and Prevention. NIOSH will observe its 40th anniversary in 2011.

More data from the study described in the blog can be found in Kardous and Morata, "Occupational and recreational noise exposures at stock car racing circuits: An exploratory survey of three professional race tracks," Noise Control Eng. J. 58(1), Jan.-Feb. 2010. Additional information about NIOSH’s findings and recommendations for preventing work-related hearing loss can be found at http://www.cdc.gov/niosh/topics/noise/